This patch replaces the environment variable "GTK_IM_MODULE" with
"GUIX_GTK3_IM_MODULE_FILE" to prevent this version of GTK+ from loading input
method modules for other major versions of GTK+.

--- gtk+-3.20.3/gtk/deprecated/gtkrc.c	2016-08-21 22:40:48.168437905 +0200
+++ gtk+-3.20.3/gtk/deprecated/gtkrc.c	2016-08-23 10:12:09.097070097 +0200
@@ -768,7 +768,7 @@
 gchar *
 gtk_rc_get_im_module_file (void)
 {
-  const gchar *var = g_getenv ("GTK_IM_MODULE_FILE");
+  const gchar *var = g_getenv ("GUIX_GTK3_IM_MODULE_FILE");
   gchar *result = NULL;
 
   if (var)